The minimum feature sizes of microelectronic devices are approaching the deep sub-micron regime to meet the demand for faster, lower power microprocessors and digital circuits. The introduction of copper (Cu) metal into multilayer metallization schemes for manufacturing integrated circuits can necessitate the use of diffusion barriers/liners to promote adhesion and growth of the Cu layers, and to prevent diffusion of Cu into the dielectric materials. Barriers/liners that are deposited onto dielectric materials can include refractory materials, such as tungsten (W), rhenium (Re), ruthenium (Ru), molybdenum (Mo), and tantalum (Ta), that are non-reactive and substantially immiscible with Cu and can offer low electrical resistivity. Current integration schemes that integrate Cu metallization and dielectric materials can require barrier/liner deposition processes that can be performed at low substrate temperatures. Another application of refractory materials in emerging microelectronic devices includes metal gate electrodes in conjunction with high-permittivity dielectric materials (also referred to herein as “high-k” materials). Metal gates are expected to provide a range of benefits for gate-stack scaling such as eliminating the poly-silicon depletion effect. Successful integration of metal layers as metal gates and metal barriers/liners in semiconductor devices requires sufficiently high deposition rates at low or moderate substrate temperatures, low electrical resistivity, low stress of the deposited metal layers, good adhesion of the metal layers to underlying and overlying materials, good thickness uniformity, low contaminant levels, and good layer morphology including low surface roughness.
A Re metal layer can be deposited by low temperature thermal chemical vapor deposition from a Re-carbonyl precursor. However, the Re-carbonyl precursor is subject to incomplete decomposition, resulting in reaction by-products that can be adsorbed into the Re metal layer or on the surface of the Re metal layer. During a subsequent exposure of the Re metal layer to ambient atmosphere, Re-oxide nodules form on the surface of the Re metal layer, where the formation of the nodules is promoted by the by-products present in the surface of the metal layer with the oxygen in air. These nodules may adversely affect the properties and morphology of the Re metal layer.
There is thus a need to avoid nodule formation on the surface of a Re metal layer upon exposure of the metal layer to oxygen.